Temporary heart assist system

ABSTRACT

A balloon is positionable in the patient&#39;s descending aorta. The balloon includes a balloon catheter and two pressure sensors that electrically couple to an extra-corporeal controller. The balloon itself also couples pneumatically to the extra-corporeal controller. An extra-corporeal pump electrically couples to the extra-corporeal controller, the pump having an outlet connectable to the patient&#39;s infra-diaphragmatic artery. The pump inlet is connectable via a cannula to the patient&#39;s supra-diaphragmatic artery.  
     A doctor inserts the balloon into the descending aorta, and positions the balloon near the level of the patient&#39;s diaphragm. A balloon catheter, coupled to the extra-corporeal controller, inflates and deflates the balloon. An electrocardiogram ECG and proximal aortic blood pressure, measured in the upper arterial compartment via a lumen in the balloon catheter, serve as inputs to cycle the balloon synchronously with the heartbeat.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is a divisional of application Ser. No.10/106,744, filed Mar. 26, 2002, and is hereby incorporated herein byreference.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

[0002] Not Applicable.

REFERENCE TO A “SEQUENTIAL LISTING,” A TABLE, OR A COMPUTER PROGRAMLISTING APPENDIX SUBMITTED ON A COMPACT DISC

[0003] Not Applicable.

BACKGROUND OF THE INVENTION

[0004] Many types of cardiac assist devices have been developed over thepast 40 years. The general types of devices can be characterized asshort-term (hours to days), bridge-to-transplantation,bridge-to-recovery, and permanent or long-term. The goal of thesedevices is to mechanically support the failing heart by increasingsystemic perfusion, and/or reducing the workload of the failing heart,thus creating the most favorable environment for cardiac recovery.

[0005] Short-term devices are used on patients whose hearts havesustained a serious injury but can recover if adequately supported. Themost commonly used short-term device is the intra-aortic balloon pump(“IABP”). Indications for employment of the IABP include cardiogenicshock or severe heart failure secondary to acute myocardial infarctionor following open-heart surgery, unstable angina resistant to drugtherapy, and refractory ventricular irritability after myocardialinfarction. *

[0006] The basic components of the intra-aortic balloon pump (“IABP”)are a catheter tipped with a long balloon and a pump console thatshuttles helium gas through the catheter to inflate and deflate theballoon synchronously with the heart beat. The balloon is inserted intoan artery and guided to a position in the descending thoracic aorta justdistal to the left subclavian artery. The pump control console containssignal processing, drive, timing, and control mechanisms for appropriateinflation and deflation. During cardiac systole ventricular contractionand ejection, the IABP is rapidly deflated, reducing the workload andoxygen demands of the heart by decreasing the resistance to blood flowfrom the ventricle. During cardiac diastole ventricular relaxation andfilling, the IABP is rapidly inflated counter-pulsation increasingaortic and coronary perfusion pressures. Timing of theinflation-deflation cycle is based on the electrocardiogram and arterialblood pressure waveform.

[0007] When heart failure is severe, the IABP cannot provide adequatecirculatory support because it cannot replace cardiac function. Thetreatment of severe heart failure requires the use of cardiac-bypassblood pumps. These devices are more invasive than the IABP and employdirect cannulation of the ventricle or atrium. Implantation and removalof the cardiac cannulas may further injure the heart and be associatedwith bleeding complications. It is estimated that nearly 100,000patients worldwide underwent short-term mechanical circulatory supportduring 2000.

[0008] Because of the limitations of aortic bypass pumps, intra-aorticballoon pumps, and the complications associated with cardiac bypasspumps, there is a need for an improved short-term heart-assist device.

FIELD OF THE INVENTION

[0009] The present invention relates generally to methods and devicesfor mechanically assisting the failing heart. More specifically, itrelates to balloon catheters and bypass pumps.

DESCRIPTION OF RELATED ART

[0010] The related art can be reviewed by the following patents. Thefull disclosures of the following patents are incorporated herein bythis reference:

[0011] The following patents disclose intra-aortic balloon pumps. Thefull disclosures of these patents are all incorporated herein by thisreference: 6,290,641 Intra-aortic balloon pump having improved automatedelectrocardiogram based intra-aortic balloon deflation timing 6,245,008Fast response intra-aortic balloon pump 6,241,706 Fast responseintra-aortic balloon pump 6,238,382 Intra-aortic balloon catheter havinga tapered Y-fitting 6,210,319 Intra-aortic balloon pump condensationprevention system 6,191,111 Method and device for enhancing of biobypassby increasing the coronary blood flow 5,817,001 Method and apparatus fordriving an intra-aortic balloon pump

[0012] The following patents disclose intra-aortic balloons. The fulldisclosures of these patents are all incorporated herein by thisreference: 6,213,975 Intra-aortic balloon catheter having an ultra-thinstretch blow molded balloon membrane 6,149,578 Piston-actionintra-aortic coronary assist device 6,024,693 Intra-aortic ballooncatheter 5,935,501 Method for making a packaging sheath for intra-aorticballoon catheters 5,928,132 Closed chest intra-aortic balloon basedventricular assist device 5,913,814 Method and apparatus for deflationof an intra-aortic balloon 5,865,721 Intra-aortic balloon catheters5,817,001 Method and apparatus for driving an intra-aortic balloon pump5,772,631 Procedure for alleviating arterial obstruction 5,759,175Intra-aortic balloon catheter 5,718,861 Method of forming intra-aorticballoon catheters 5,697,906 Intra-aortic balloon catheter 5,683,347Balloon catheter 5,618,270 Transthoracic aortic sleeve 5,599,329 Multipurpose perfusion cannula 5,524,757 Packaging sheaths for intra-aorticballoon catheters 5,460,607 Balloon catheter 5,456,665 Intra-aorticballoon catheter RE34,993 Method of inserting a lab device into the body5,413,549 Devices and methods for efficient intra-aortic balloon pumping5,330,451 Multi purpose perfusion cannula 5,230,692 Intra-aortic balloonpump 5,158,529 Pumping device for operating an intra-aortic balloon5,120,299 Intra-aortic balloon assembly with hemostasis device 4,994,018Intra-aortic balloon assembly 4,901,707 Prepackaged intra-aortic balloonassembly with holder, and method of using same 4,897,077 Method ofinserting an IAB device into the body 4,827,906 Apparatus and method foractivating a pump in response to optical signals from a pacemaker4,809,681 Electrocardiographic measurement method for controlling anintra-aortic balloon pump 4,804,358 Coronary perfusion pump 4,733,652Intra-aortic balloon 4,697,573 Percutaneous intra-aortic balloon andmethod for using same 4,644,936 Percutaneous intra-aortic balloon andmethod for using same 4,576,142 Percutaneous intra-aortic balloon andmethod for using same 4,552,127 Percutaneous intra-aortic balloon havingan EKG electrode and a twisting stylet for coupling the EKG electrode tomonitoring and/or pacing instrumentation external to the body 4,531,512Wrapping system for intra-aortic balloon utilizing a wrapping envelope4,522,195 Apparatus for left heart assist 4,522,194 Method and anapparatus for intra-aortic balloon monitoring and leak detection4,515,587 IAB having apparatus for assuring proper balloon inflation anddeflation 4,473,067 Introducer assembly for intra-aortic balloons andthe like incorporating a sliding, blood-tight seal 4,467,790Percutaneous balloon 4,444,186 Envelope wrapping system for intra-aorticballoon 4,422,447 Percutaneous balloon 4,407,271 Apparatus for leftheart assist 4,402,307 Balloon catheter with rotatable energy storingsupport member 4,362,150 Percutaneous intra-aortic balloon apparatus4,346,698 Balloon catheter with rotatable support 4,327,709 Apparatusand method for the percutaneous introduction of intra-aortic balloonsinto the human body 4,311,133 Intra-aortic balloon 4,287,892 Cannula forintra-aortic balloon devices and the like 4,276,874 Elongatable ballooncatheter 4,261,339 Balloon catheter with rotatable support 4,122,858Adapter for intra-aortic balloons and the like 4,080,958 Apparatus foraiding and improving the blood flow in patients 3,985,123 Method andmeans for monitoring cardiac output

[0013] Aortic occlusion balloons are known in the prior art. Such aorticballoons are non co-pulsating with the heartbeat and are not employedwith an aortic bypass pump. The following patents disclose aorticocclusion balloons. The full disclosures of these patents are allincorporated herein by this reference: 6,254,563 Perfusion shuntapparatus and method 6,248,086 Method for cannulating a patient's aorticarch and occluding the patients ascending aortic arch 5,413,558Selective aortic perfusion system for use during CPR 5,216,032 Selectiveaortic arch perfusion using perfluorochemical and alpha-adrenergicagonist to treat cardiac arrest 5,195,942 Cardiac arrest treatment4,697,574 Pump for assistance in circulation 4,531,936 Device and methodfor the selective delivery of drugs to the myocardium

[0014] The following patents disclose cardiac bypass pumps. The fulldisclosures of these patents are all incorporated herein by thisreference: 6,238,334 Method and apparatus for assisting a heart to pumpblood 6,149,683 Power system for an implantable heart pump 6,099,460Electromagnetic head-assist technique and apparatus 6,015,434 Artificialheart pump 5,588,812 Implantable electric axial-flow blood pump5,443,503 Artificial heart pump 5,344,443 Heart pump

[0015] Aortic bypass pumps are known in the prior art. Aortic bypasspumps are not employed with a co-pulsating aortic occlusion balloon forheart assistance. The following patents disclose aortic bypass pumps.The full disclosures of these patents are all incorporated herein bythis reference: 6,299,575 Implantable heart assist system 6,200,260Implantable heart assist system 5,749,855 Catheter pump 4,968,293Circulatory assist device

BRIEF SUMMARY OF THE INVENTION

[0016] A preferred embodiment of the present invention provides a methodand a system to temporarily assist the failing heart. The temporaryheart-assist system comprises an occluding device positionable in thepatient's descending aorta. The occluding device may or may not includea pressure sensor that electrically couples to an extra-corporealcontroller. The occluding device itself also couples pneumatically tothe extra-corporeal controller. The pump inlet of an extra-corporealpump is connectable via a cannula to a patient's supra-diaphragmaticartery. The pump outlet of the extra-corporeal pump is connectable via acannula to a patient's infra-diaphragmatic artery.

[0017] In the method of the present invention, a doctor inserts into thepatient the occluding device via a peripheral artery into the descendingaorta, and positions the occluding device near the level of thepatient's diaphragm. The occluding device catheter, coupled to theextra-corporeal controller, inflates and deflates the occluding device.The electrocardiogram ECG and proximal aortic blood pressure, measuredin the upper arterial compartment via a lumen in the occluding devicecatheter, serve as inputs to cycle the occluding device synchronouslywith the heartbeat. The step of inflating occurs just prior to the startof cardiac systole co-pulsation and ventricular ejection. Theextra-corporeal pump continuously or cyclically pumps blood from asupra-diaphragmatic-artery to a infra-diaphragmatic artery. The pumpingflow rate varies in response to the end-systolic pressure measured inthe upper arterial compartment of the patient's body. The step ofdeflating the aortic balloon occurs at the start of cardiac diastole andaortic valve closure. Deflating the balloon stabilizes the perfusionpressure between the upper and lower arterial compartments.

[0018] In another feature of the present invention, the method of thepresent invention pumps blood from the patient's upper to the patient'slower arterial compartments.

[0019] The present invention is designed to temporarily assist thefailing human heart for a period of several hours to several days. Theobjectives of the heart-assist system of the present invention are toaugment cardiac output and enhance systemic perfusion, reduce theworkload and oxygen requirements of the acutely failing heart and allowfor its recovery, allow for optimization of concomitant drug therapy,require minimal surgical intervention for insertion and removal, andreduce additional trauma to the failing heart by eliminating a need fordirect cannulation of the left atrium or left ventricle. An additionalfeature of this technology is enhancement of diastolic perfusion byelevation of pressure throughout the diastolic interval and, unlike acommercially available balloon pump, enhancement of perfusion to allorgans.

[0020] The present invention allows for treatment of the failing heartin a minimally invasive manner with augmentation of left ventricularstoke volume cardiac output and simultaneous reduction in leftventricular workload and oxygen requirements of the heart.

[0021] An important feature of the invention is that it rapidly inflatesa small-volume balloon, partially occluding the aorta just prior to thestart of cardiac systole and ventricular ejection. In another feature ofthe invention, it regulates aorta-aorta bypass blood pump flow to obtaina specific end-systolic aortic pressure measured in the upper arterialcompartment. In another feature of the invention, decreasingend-systolic aortic pressure results in an increased ventricular strokevolume based on the ventricular pressure-volume-contractilityrelationship. Decreased systolic pressure also reduces the workload onthe failing heart. Increased bypass pump blood flow elevates perfusionpressure in the lower arterial compartment. In another feature of theinvention, during ventricular diastole, the system rapidly deflates anaortic balloon at end-systole. Deflating the aortic balloon stabilizesthe perfusion pressure between the upper and lower arterialcompartments.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0022]FIG. 1 depicts an overview of the temporary heart-assist system,illustrating the intra-aortic balloon, aortic-aortic external bypasspump, and external controller, as installed on a patient.

[0023]FIG. 2 is a detailed view of the intra-aortic balloon andassociated catheter, illustrating some of their features.

[0024]FIG. 3A is a schematic of the temporary heart-assist system,illustrating the intra-aortic balloon, aortic-aortic external bypasspump, and external controller, as installed on a patient.

[0025]FIG. 3B is a schematic of a human heart, depicting part of aninlet catheter with the tip of the catheter positioned through theaortic valve into the left ventricle.

[0026]FIG. 4 is a graph of the leftventricular-pressure-volume-contractility relationships for the normalheart, failing heart, and failing heart supported with the temporaryheart-assist system according to the present invention.

[0027]FIG. 5A is a graph showing the electrocardiogram and aortic bloodpressures of the failing heart.

[0028]FIG. 5B and FIG. 5C are graphs showing the electrocardiogram,aortic blood pressures, aortic balloon inflation/deflation timing, andbypass pump flow rate or motor speed with the temporary heart-assistsystem operating.

[0029]FIG. 6A is a schematic of the external control unit illustratingmanual controls, transducer inputs, monitor display, aortic balloonpneumatics, and bypass pump electronics.

[0030]FIG. 6B is a schematic of the assist timing control panel,illustrating the method for setting the inflation and deflation timingof the aortic balloon.

[0031]FIG. 6C is a schematic of the pressure assist control panel,illustrating the method for setting the degree of systolic pressureunloading of the heart.

[0032]FIG. 6D is a detailed graph showing the control-logic loop for theheart assist system.

DETAILED DESCRIPTION OF THE INVENTION

[0033] In the drawings, like numerals designate like parts throughoutthe drawings. In FIG. 1, a temporary heart-assist system 7 isillustrated in use with a human heart. The heart-assist system 7includes an occluding device, or balloon, 8 in the patient's aorta,connected to a controller 9, Which in turn connects to an extracorporealaortic bypass blood pump 10.The occluding device 8 can be any devicethat can be remotely opened and closed, either partially or fully, butin the preferred embodiment is a balloon. U.S. Pat. Nos. 5,894,273 and6,137,416 disclose a limited-use controller that does not control anintra-aortic valve, such as the balloon 8. Such a controller could beused to control the aortic bypass blood pump 10. The deflated balloon 8is mounted on the end of a flexible catheter 11. The balloon 8 andcatheter 11 are inserted into the aorta via a peripheral artery,preferably at a point 12 on the femoral artery. The catheter 11may beinserted percutaneously over a guide wire or surgically by directexposure of the vessel. The balloon 8 is positioned in the descendingthoracic aorta at approximately the level of the diaphragm. Morespecifically, the balloon 8 is placed above the diaphragm, but below thesubclavian artery.

[0034] Referring now to FIG. 2, the aortic blood pressure AoP isrecorded with two pressure transducers, or sensors 13 on the balloon 8.The pressure transducers 13 are conventional transducers, such as modelnumber BP01, manufactured by the InvenSys Company located in Milpitas,Calif. The controller 9 allows sustained flow to pump and reads upperand lower pressure for pump adjustments from the balloon sensors 13. Theballoon sensors 13 monitor pressure, and when pressure goes up then pumpflow increases, and vice versa. The principle of the balloon 8 is toequalize pressure during systole, and to auto-regulate the flow rate ofthe pump 10, based on the pressure sensed by the pressure sensors 13 oneither side of the balloon 8. The balloon 8 inflates as the aortic valveopens and deflates upon closure. If timed properly, there should be noperiod in which the aortic valve is closed and the balloon 8 inflated.In an alternate embodiment, only one sensor 13 is used.

[0035] The catheter 11 has duel lumens. A larger lumen 14 is used toshuttle gas to and from the balloon 8 via openings or ports 15 locatedon a catheter wall. A smaller lumen 16 runs continuously through thebody of the catheter 11. The smaller lumen 16 is used for inserting thecatheter 11 over an aortic guide wire and as a pressure transmissiontube for the continuous measurement of central aortic pressure AoPproximal to the balloon 8 during operation of the heart-assist system10. The balloon 8 and catheter 11 are made of biocompatible polymericmaterials. The balloon 8 and catheter 11 are flexible and nontraumaticto the aorta, but have a wall thickness and strength sufficient towithstand cyclic rapid balloon inflation and deflation.

[0036] The pressure transducers 13 connect to the pressure transmissiontube lumen 16. The lumen 16 couples to a cable 18 that connects to thecontroller 9. The balloon 8 is inflated and deflated by gas pressure,preferably using helium gas, supplied through a pneumatic tube 20attached to the large lumen 14. The tube 20 connects to the controller9. The balloon 8 deflates when depressurized with gas, and inflates whenpressurized with gas, thereby partially or fully occluding the aorta. Toavoid stagnation of the blood and vessel trauma, the balloon 8 does notneed to completely occlude the descending aorta; it may leave some spaceon either side.

[0037] Referring now to FIG. 3A, the left ventricle 22 of the heart isshown in systole with ejection of blood (long arrow) through the openedaortic outflow valve 24 into the ascending aorta 26. An inlet cannula 38for the pump 10 is inserted into the aorta at a point 40 proximal to theballoon 8, using conventional surgical techniques. The point 40 may bein the ascending aorta 26, for patients who have an open chest, or maybe in a branch vessel, preferably the subclavian artery, for patientswhose chest is not open, or at any point between.

[0038] Referring now to FIG. 3B, in an alternate embodiment, the lengthof the inlet cannula 38 extends with its tip positioned through theaortic valve 24 into the left ventricle 22. Holes 39 along the length ofthe inlet cannula 38 in the aorta, combined with a hole 39 in the tip ofthe cannula 38, provide direct unloading of the left ventricle 22, plusafterload reduction in the aorta.

[0039] The lumen of the inlet cannula 38 is of sufficient size andcapacity to allow flow rates (see arrow) up to 7 liters per minute, withminimal pressure drop and blood destruction hemolysis. U.S. Pat. No.6,007,478 discloses a cannula having constant wall thickness withincreasing distal flexibility. The full disclosure of this patent isincorporated herein by this reference. The inlet cannula 38 is broughtout of the patient and connected to the pump 10. The pump 10 is acommercially available non-pulsatile blood pump. Artificial heart pumpscan be classified into the diaphragm type, the tube type, the rollerpressure type, and the radial flow type that operates by rotationalmotion. Typical of the radial flow type is the centrifugal type. Thefollowing U.S. Patents disclose centrifugal heart pumps: 5,894,273Centrifugal blood pump driver apparatus 6,015,434 Artificial heart pump6,137,416 Method of controlling centrifugal pump 6,227,817Magnetically-suspended centrifugal blood pump

[0040] The full disclosures of these patents are all incorporated hereinby this reference. The pump 10 may be any radial pump, but in thepreferred embodiment the pump 10 is a centrifugal pump. A drive motor 42powers the pump 10 via a magnetic coupling 44 located between the drivemotor 42 and the pump 10. The pump 10 has the capacity to pump up to 7liters per minute of blood without increased hemolysis or thrombosisclot formation. Pump flow rate is continuously measured using aconventional flow transducer 45 connected to the controller 9. Thetransducer 45 may be of the ultrasonic or electromagnetic type, but inthe preferred embodiment is an ultrasonic model, made by TransonicSystems, Inc., located in Ithaca, N.Y. Blood returns to the patient viaan outlet cannula 46 inserted in an infra-diaphragmatic artery at apoint 48 far from the balloon 8, using conventional surgical techniques.Preferably, the point 48 is in the femoral artery. The lumen of theoutlet cannula 46 is of sufficient size and capacity to allow flow ratesup to 7 liters per minute, with minimal pressure drop and hemolysis.

[0041] An electrocardiogram (“ECG”) is recorded via electrodes 50 placedon the skin of the patient. The electrodes couple to cables 52 thatconnect to the controller 9.

[0042] The pump drive motor 42 couples to the controller 9 via a cable62. The purpose of the pump 10 is to pump blood from the upper arterialcompartment 14 to the lower arterial compartment. During ventricularsystole, and using. the ECG and aortic pressure-triggered controller 9,the small-volume balloon 8 is rapidly inflated, partially occluding theaorta. In the preferred embodiment, the flow rate of the pump 10 isregulated to obtain a specific end-systolic AoP in the upper arterialcompartment (aorta 26). However, in an alternate embodiment, the pumpruns continuously at a set speed. A deceased end-systolic aorticpressure afterload results in an increase in cardiac output blood flow.Decreased afterload also reduces the workload and oxygen consumption ofthe failing heart. Increased systemic blood flow also elevates perfusionpressure in the lower arterial compartment. During ventricular diastole,the balloon 8 rapidly deflates, thereby increasing the perfusionpressure throughout the arterial compartment 26. The pump flow rate canalso be slowed during diastole by coasting or braking the motor 42,thereby reducing the potential for blood trauma hemolysis. Decreasingpump flow may be obtained by coasting or braking the speed of thecentrifugal pump motor. In an alternate embodiment, the pump 10 runscontinuously at a set speed.

[0043] Referring now to FIG. 4, the y-axis shows ventricular pressure0-120 mmHg, and the x-axis shows ventricular volume 0-210 ml. An exampleof the pressure-volume relationship is shown for the normal N heart.Starting at the ventricular end-diastolic volume EDV for the normalheart N, the loop moves in a counter-clockwise direction. First theventricle contracts and generates pressure sufficient to open the aorticvalve AVO. The ventricle ejects blood into the aorta and the ventricularvolume decreases. The ventricular stoke volume for each cardiac cycle iscalculated by the formula: stoke volume ml/beat=EDV−ESV. At end-systolethe aortic valve closes and pressure decreases as the walls of theventricle relax during diastole. Following opening of the mitral valveMVO the left ventricle fills from the left atrium, containing oxygenatedblood from the lungs, and ventricular volume increases. Contractilitystrength of contraction of the normal ventricle may be defined by theslope of the end-systolic pressure ESP-volume ESV relationship shown assolid line CN. Thus, for a given EDV, cardiac stroke volume decreaseswith increasing ESP and ESV. Conversely, stroke volume increases withdecreasing ESP and ESV for a given EDV and contractility slope. Withacute heart failure, the pressure-volume loop F1 is shifted downward andto the right. For this heart failure example, the contractility slopeshown as dashed line CF is reduced and the EDV is increased. Despite theincrease in EDV and decrease in ESP, the cardiac stroke volume isreduced due to decreased contractility slope. Because of the decreasedcontractility slope, the ventricle is more sensitive to changes in theESP. Otherwise stated, with heart failure small changes in ESP lead tolarger changes in ESV compared to the normal ventricle.

[0044]FIG. 4 also illustrates the effects of the embodiments of thepresent invention on the failing heart. With actuation of the aorticballoon 8 and the aortic-aortic bypass pump 10, the left ventricle ispressure and volume unloaded. During ventricular systole, the aorticballoon 8 is inflated, occluding the aorta, and the bypass blood pump 10transfers blood from the upper arterial compartment to the lowerarterial compartment. Pump flow rate is controlled increased ordecreased to result in a set ESP level. Compared to the unassistedcondition loop F1, the reduced ESP during mechanical assistance resultsin a reduced ESV loop F2 despite an unchanged contractility slope dashedline CF. Thus, reducing ESP and ESV with the heart-assist system 7 willincrease cardiac stroke volume systemic perfusion and may also decreaseventricular EDV. Pressure and volume unloading of the ventricle alsodecreases systolic ventricular wall tension a primary component ofcardiac muscle oxygen consumption.

[0045] The aortic balloon 8 and aortic bypass pump 10 (axial orcentrifugal flow device) are synchronously operated using theECG-triggered and pressure-feedback controller 9. During ventricularsystole the small-volume balloon 8 is rapidly inflated, partiallyoccluding the aorta. The flow rate of the aortic bypass blood pump 10 isregulated to obtain a specific end-systolic aortic pressure in the upperarterial compartment. A decreased end-systolic aortic pressure providedby the blood pump results in ventricular unloading and augmentation ofsystemic perfusion (stroke volume and cardiac output). The pump 10assumes the circulation to the lower half of the body and the weakenedheart is responsible for the upper half of the body only. Decreasedafterload also reduces the workload on the failing heart. The increasedsystemic blood flow elevates perfusion pressure in the lower half of thebody. During ventricular diastole, the balloon is deflated and thepump-generated pressure and flow increases the perfusion pressurethroughout the arterial tree. Compared to the prior art intra-aorticballoon pumps, the invention provides greater augmentation of systemicperfusion, improved direct ventricular unloading, and increaseddiastolic perfusion, and without direct cannulation of the leftventricle or atrium as required for cardiac bypass devices.

[0046] Because of aortic occlusion, the pump 10 flows from high pressureto lower pressure and will actually assume about 60% of the work. It isimportant to note that the pump 10 makes diastole become active. Thepump 10 achieves systolic unloading by augmenting flow and increasedblood flow during diastolic which reduces load to the heart.

[0047]FIG. 5A and 5b illustrate the functioning of the heart-assistsystem 7. FIG. 5A shows the ECG and AoP for the heart failure conditionwith the assist system 7 off. The ECG is recorded from skin electrodesappropriately placed on the patient. The R-wave 75 of the ECGcorresponds with the start of ventricular systole and is used as acontrol trigger. The AoP shows the pressure recorded in the proximalaorta solid line and distal aorta dashed line. With the assist systemoff and the aortic balloon deflated, the proximal and distal aorticpressures are essentially equal. The start of systole 78 correspondswith the EDP time. The end of systole 79 corresponds with the ESP time.The systolic period S is when left ventricular ejection into the aortaoccurs. The diastolic period D is when the ventricle relaxes andcoronary perfusion occurs.

[0048] Referring now to FIG. 5B and FIG. 5C, ,with the heart assistsystem 7 on, the aortic balloon is activated in two stages: inflationduring ventricular systole S and deflation during cardiac diastole D. Asshown in FIG. 5B and FIG. 5C, the R-wave of the ECG is used to triggerballoon inflation. The start of balloon inflation 90 is controlled toobtain a preset EDP level measured in the proximal aorta using thepressure transmission lumen 16 of the aortic catheter 11. Duringinflation the balloon 8 makes uniform and firm contact with the insidewall of the aorta. This has the effect of blocking the downstream flowof blood in the aorta during systole. Thus, a closed volume is createdbetween the outflow valve of the ventricle and the expanded balloon 8.

[0049] At the time of systolic S balloon inflation 90, the aortic bypasspump shunts blood from the upper arterial compartment proximal aorta tothe lower arterial compartment distal aorta. The centrifugal blood pumpflow rate and RPM are regulated by the external controller 9 to obtain apreset ESP level measured in the aorta proximal to the inflated balloon.Thereby, the proximal aortic pressure is decreased solid line 80 and thedistal aortic pressure is increased dashed line 82 during systole Scompared to the unassisted condition shown in FIG. 5A. At the end ofsystole start of diastole, the aortic balloon is rapidly deflated 92.Thus the aorta is opened between the upper and lower arterialcompartments, and the two pressures equilibrate. The equilibrationresults in increased proximal solid line 84 and distal dashed line 86aortic pressures during diastole D compared to the unassisted conditionillustrated in FIG. 5A. Therefore, the heart-assist system described inthe present invention is capable of increasing cardiac stroke volume andsystemic perfusion, reducing ventricular workload and oxygenconsumption, and increasing perfusion pressure to the coronary arteriessupplying the heart. Also shown in FIG. 5B and FIG. 5C, the flow rateand RPM of the centrifugal aortic-aortic bypass pump may be increased 94at the time to correspond 95 with aortic balloon inflation 90. Thisprovides for maximum pressure and volume unloading of the ventricle 80and augmentation of distal perfusion pressure 82. Additionally, the flowrate and RPM of the centrifugal blood pump may be decreased 97 at thetime to correspond 98 with aortic balloon deflation 92. The reduced flowrate may decrease the degree of pump-induced hemolysis.

[0050]FIG. 6A illustrates the components of the heart-assist systemcontrol unit 9. Manual controls 100 are used to set the timing ofballoon inflation and deflation, and to set the degree of pressureassist provided by the centrifugal blood pump. The control unit containspreamplifiers 102 with EKG 52, aortic pressure 18, and pump flow 45inputs. Control setting and transducer signals are passed through an A/Dconverter 104 with before being sent to the processor unit 106 andmonitor display subsystem 108. Based on transducer signals and controlsettings, the processor unit controls and monitors the pneumaticsubsystem 110 that provides gas pressure and vacuum to inflate anddeflate the aortic balloon, respectively, via a pneumatic drive line 20.Processor unit 106 contains a microprocessor such as a Motorola 68HC11,random access memory (RAM) and program memory (PROM) which containssoftware to control the system. The processor unit also controls andmonitors the motor control subsystem 112, that sends power to thecentrifugal blood pump drive motor via a electronic cable 64.

[0051]FIG. 6B illustrates the timing control panel 114, on the externalcontrol unit, that is used for setting aortic balloon AoB inflation 116and deflation 118 timing with respect to the R-wave of theelectrocardiogram 75 as a percentage of the R-R time interval. With theassist pump and balloon turned off, the aortic balloon inflation time isestablished by manually moving the slide control 120 that controls acursor line 122 simultaneously shown on the monitor display 108. Theslide control is moved such that the cursor line corresponds withend-diastole ED and the ED pressure 124 overlying the displayed aorticpressure waveform 126. Additionally, balloon deflation time isestablished by manually moving the slide control 128 that controls asecond cursor line 130 on the display monitor. The slide control ismoved such that the cursor line corresponds with end-systole ES and theES pressure 132 for the aortic pressure waveform. In the event thatheart rate changes by +10 beats per minute, the assist pump and balloonshould be turned off and the inflation and deflation timingreestablished.

[0052]FIG. 6C illustrates the pressure assist Pa control panel 140, onthe external control unit, that is used for setting the degree ofventricular unloading provided by the aortic bypass pump. The degree ofventricular unloading is determined by the measured difference betweenthe aortic end diastolic pressure EDP 142 and the end systolic pressureESP 144. A control knob 146 is manually set to establish the degree ofpressure unloading which ranges from a negative 5 mmHg to a positive 5mmHg. A control knob setting of 0 corresponds with the ESP=EDP. Thissetting provides a moderate level of ventricular unloading and heartassist. A setting of −5 corresponds with the ESP being 5 mmHg less thanthe corresponding EDP. This setting provides the maximum level ofventricular unloading and heart assist. A setting of +5 corresponds withthe ESP being 5 mmHg more than the EDP. This setting provides theminimum level of ventricular unloading and is used for weaning from theheart assist system. The illustrated control method allows forbeat-to-beat control of pump flow rate regardless of changes in thesystemic vascular resistance and blood pressure. A manual push button148 must be depressed simultaneously with changing the control knobsetting. This method is used to prevent inadvertent changes in thepressure assist setting.

[0053]FIG. 6D is a detailed flow diagram of the heart-assist systemcontrol logic 150. Beat to beat control of the aortic occlusion balloonand aortic bypass pump is started with electrocardiogram R-wavedetection 152. With R-wave detection the timing clock and monitordisplays are reset and the preceding R-R interval time is measured 154.Based on the percentage ED and ES control setting 156 shown in FIG. 7,the ED and ES times in seconds is calculated 158 for the measured R-Rinterval 154. Aortic balloon inflation IT and deflation DT times 160 arecalculated by subtracting a known electromechanical delay time for thepneumatic subsystem from the previously calculated ED and ES times 158,respectively. At the calculated balloon inflation time IT followingR-wave detection, a trigger signal 162 is sent to the pneumaticsubsystem 110 to provide drive gas to the aortic balloon. At thecalculated ED time, the ED pressure EDP is measured 164 from the aorticpressure input signal. Based on the pressure assist control settingshown in FIG. 8, the calculated ES pressure ESPc 168 is determined usingthe formula: ESPc=measured EDP 164 minus the pressure assist Pa setting146. At the calculated balloon deflation time DT following R-wavedetection, a trigger signal 170 is sent to the pneumatic subsystem 110to exhaust drive gas from the aortic balloon. At the calculated ES time,the ES pressure ESP is measured 172 from the aortic pressure inputsignal.

[0054] The calculated pressure difference Pdif 174 is determined usingthe formula: Pdif=measured ESP 172 minus the calculated ESPc 168. Thebypass pump speed RPM change is determined 176 based on the calculatedPdif 174. Positive Pdif values result in increasing pump speeds.Conversely, negative Pdif values result in decreasing pump speeds. Aspeed control change signal 178 is sent to the motor control subsystem112 which regulates centrifugal pump flow. Following the above steps,the control logic unit waits for the next R-wave detection 180.

[0055] Thus, the invention provides a method and apparatus for assistingthe failing heart until such time that ventricular recovery and weaningfrom the assist system occurs. There are several advantages of thisinvention over prior intra-aortic balloon pump and ventricular assistdevices. The invention is particularly useful in increasing cardiacoutput and decreasing ventricular loading without direct cannulation ofthe left atrium or left ventricle. The method includes controlledintermittent occlusion of the aorta synchronously with the cardiaccycle, accompanied by the pumping of blood from the proximal to thedistal aorta at a rate sufficient to pressure and volume unload thefailing left ventricle. Systolic ventricular unloading increases cardiacoutput and decreases myocardial oxygen demands. Augmented cardiac outputlevels also increase perfusion of the coronary arteries supplyingoxygenated blood to the heart.

[0056] Although the preferred embodiment of the present invention hasbeen described above, it will be understood by those skilled in the artthat numerous modifications from the present invention may be madewithout departing from the scope and meaning of the claims that follow.

What is claimed is:
 1. A method for temporarily assisting a heart of apatient, the patient wearing ECG sensors with attached electrodes, themethod comprising the steps of: a. inserting an occluding device, havinga pressure sensor, into the patient's descending aorta; b. positioningthe occluding device near the level of the patient's diaphragm; c.coupling the occluding device to an extra-corporeal controller; and d.opening and closing the balloon in response to signals from the ECGelectrodes.
 2. The method of claim 1, wherein the step of closing occursjust prior to the start of cardiac systole and ventricular ejection. 3.The method of claim 2, further comprising the step of using anextra-corporeal pump to continuously pump blood from a patient'ssupra-diaphragmatic artery to an infra-diaphragmatic artery.
 4. Themethod of claim 3, wherein in the step of continuously pumping blood,the pumping flow rate varies in response to the end-systolic pressuremeasured in the upper arterial compartment of the patient's body.
 5. Themethod of claim 4, wherein the extra-corporeal controller a) causes theoccluding device to intermittently occlude the aorta, synchronously withthe patient's cardiac cycle, and b) causes the extra-corporeal pump topump blood from the patient's proximal to the distal aorta at a ratesufficient to pressure and volume unload the patient's failing leftventricle.
 6. The method of claim 5, wherein the extra-corporealcontroller decreases the flow rate and RPM of the extra-corporeal pumpwhen it opens the occluding device.
 7. The method of claim 6,. whereinan inlet cannula of the extra-corporeal pump is inserted through anaortic valve into the left ventricle, the inlet cannula having holesalong a length of it positioned in the aorta, and a hole in a tip, whichis positioned in the left ventricle, for providing direct unloading ofthe left ventricle, and after-load reduction in the aorta.
 8. A methodfor temporarily assisting a heart of a patient, the patient wearing ECGsensors with attached electrodes, the method comprising the steps of: a.inserting a balloon, having a balloon catheter and two pressure sensors,into the patient's descending aorta; b. positioning the balloon near thelevel of the patient's diaphragm; c. coupling the balloon catheter to anextra-corporeal controller; d. inflating the balloon in response tosignals from the ECG electrodes, and the two pressure sensors; and e.deflating the balloon in response to signals from the ECG electrodes,and the two pressure sensors.
 9. The method of claim 8, wherein the stepof inflating occurs just prior to the start of cardiac systole andventricular ejection.
 10. The method of claim 9, further comprising thestep of using an extra-corporeal pump to continuously pump blood from apatient's supra-diaphragmatic artery to an infra-diaphragmatic artery.11. The method of claim 10, wherein in the step of continuously pumpingblood, the pumping flow rate varies in response to the end-systolicpressure measured in the upper arterial compartment of the patient'sbody.
 12. The method of claim 11, wherein the extra-corporeal controllera) causes the balloon to intermittently occlude the aorta, synchronouslywith the patient's cardiac cycle, and b) causes the extra-corporeal pumpto pump blood from the patient's proximal to the distal aorta at a ratesufficient to pressure and volume unload the patient's failing leftventricle.
 13. The method of claim 12, wherein the extra-corporealcontroller decreases the flow rate and RPM of the extra-corporeal pumpwhen it deflates the balloon.
 14. A method for temporarily assisting aheart of a patient, the patient wearing ECG sensors with attachedelectrodes, and the patient also having an intra-aortic occluding devicehaving two pressure sensors, the method comprising the steps of: a.opening and closing the intra-aortic occluding device by anextra-corporeal controller in response to signals from the ECGelectrodes and the two pressure sensors; and b. continuously pumpingblood by an extra-corporeal pump from a patient's supra-diaphragmaticartery to an infra-diaphragmatic artery
 15. The method of claim 14,wherein the step of closing occurs just prior to the start of thepatient's cardiac systole and ventricular ejection.
 16. The method ofclaim 15, wherein the pumping flow rate varies in response to theend-systolic pressure measured in the upper arterial compartment of thepatient's body.
 17. The method of claim 16, wherein the extra-corporealcontroller a) causes the occluding device to intermittently occlude theaorta, synchronously with the patient's cardiac cycle, and b) causes theextra-corporeal pump to pump blood from the patient's proximal to thedistal aorta at a rate sufficient to pressure and volume unload thepatient's failing left ventricle.
 18. The method of claim 11, whereinthe extra-corporeal controller decreases the flow rate and RPM of theextra-corporeal pump when it opens the occluding device.
 19. A methodfor temporarily assisting a heart of a patient, the patient wearing ECGsensors with attached electrodes, and the patient also having anintra-aortic balloon having two pressure sensors, the method comprisingthe steps of: a. inflating the intra-aortic balloon by anextra-corporeal controller in response to signals from the ECGelectrodes and the two pressure sensors; b. deflating the intra-aorticballoon by an extra-corporeal controller in response to signals from theECG electrodes and the two pressure sensors; and c. continuously pumpingblood by an extra-corporeal pump from a patient's supra-diaphragmaticartery to an infra-diaphragmatic artery.
 20. The method of claim 19,wherein the step of inflating occurs at the onset or during thepatient's cardiac systole and ventricular ejection.
 21. The method ofclaim 20, wherein the pumping flow rate varies in response to theend-systolic pressure measured in the upper arterial compartment of thepatient's body.
 22. The method of claim 21, wherein the extra-corporealcontroller a) causes the balloon to intermittently occlude the aorta,synchronously with the patient's cardiac cycle, and b) causes theextra-corporeal pump to pump blood from the patient's proximal to thedistal aorta at a rate sufficient to pressure and volume unload thepatient's failing left ventricle.
 23. The method of claim 22, whereinthe extra-corporeal controller decreases the flow rate and RPM of theextra-corporeal pump when it deflates the balloon.